Source: Association of Bay Area Governments, 2005 http://quake.abag.ca.gov/mitigation/pickcrit.html   Earthquakes Also Cause Damage in Other Ways... Although most earthquake damage is caused by shaking, other damaging effects of quakes can be just as devastating. For example, in the Great 1906 earthquake, the shaking damage in San Francisco was followed by fires that raged through the city almost uncontrolled, in part because water mains had broken in the quake. These and other destructive effects of quakes are discussed below.

Fires Earthquakes in urban areas are often followed by destructive fires because (1) gas lines break, (2) electrical shorts ignite fires, (3) damaged water tanks and broken pipes limit water for firefighting, and (4) clogged roads and collapsed bridges prevent firefighter access. These factors can lead to fires spreading, causing extensive additional damage and burning entire neighborhoods. This photo shows fires in San Francisco's Marina District following the 1989 magnitude 6.9 Loma Prieta earthquake (photo courtesy of CBS 5).

Damaged bridges, pipelines, powerlines, and roads Earthquakes often damage roads, hindering rescue and recovery efforts and causing accidents. Water and sewer pipeline breaks result in water loss and can cause "sinkholes" that undermine roads and buildings. Damage to natural gas and electrical distribution systems can cause fires, as well as major service outages. This car crashed when a section of the eastern span of the San Francisco-Oakland Bay Bridge collapsed in the 1989 magnitude 6.9 Loma Prieta earthquake (Earthquake Engineering Research Institute photo).

Dam failures Earthquake shaking can cause dams to fail, potentially causing catastrophic downstream flooding and reduced water supplies. In addition, many dams provide hydroelectric power, which could be critically needed following a quake. Cracks in the top of this dam were caused by the 1989 magnitude 6.9 Loma Prieta earthquake (USGS photo).

Hazardous material releases Earthquake damage can cause releases of hazardous materials from refineries and other chemical storage and distribution systems, research and industrial laboratories, manufacturing plants, and railroad tank cars. Oil was released and caught fire when this storage facility was damaged by the 1999 magnitude 7.4 Izmit, Turkey, earthquake (photo by Kandilli Observatory and Earthquake Institute).

Don't be fooled! -- Myth number 2 "AND THE EARTH OPENED..."

A popular literary device is a fault that opens during an earthquake and then closes to swallow up an inconvenient character. Unfortunately for principled writers, such "carnivorous" faults exist only in novels and B-movies.

Landslides Earthquakes can trigger landslides that damage roads, buildings, pipelines, and other infrastructure. Steeply sloping areas underlain by loose or soft rock are most susceptible to earthquake-induced landslides. This home was destroyed when the hillside beneath it gave way following the 1994 magnitude 6.7 Northridge earthquake (FEMA photo).

Liquefaction Earthquake shaking can cause soils to behave like a liquid and lose their ability to support structures. Liquefaction often causes buried gas and water lines to break. The highest hazard is in low-lying areas where there are loose, sandy soils or poorly compacted artificial fill. This photo shows liquefaction-related damage in the Marina District of San Francisco following the 1989 magnitude 6.9 Loma Prieta earthquake (USGS photo).

Surface rupture Fault movements can break the ground surface, damaging buildings and other structures. This fence near Point Reyes was offset 8 feet ( 2.5 m) when the San Andreas Fault moved in the Great (magnitude 7.8) 1906 earthquake (USGS photo).

Tsunamis Great earthquakes occurring anywhere in the Pacific Ocean may displace the ocean floor, generating tsunamis that could affect the California coast. Some coastal communities are designating Tsunami Hazard Zones and planning evacuation routes. Although the tsunami hazard in most of the Bay Area is low, coastal areas are still at risk. For example, this bait shop (Hazel's Fish Stand) in Half Moon Bay was ruined when it was hit by debris in the tsunami generated by the 1946 (magnitude 8) Alaska earthquake (photo copyright by MS & SB Collection).

Map Showing Seismic Hazard Zones This map of part of the Oakland area shows regulatory zones defined by the California Geological Survey (CGS) for three seismic hazards&emdash;earthquake-induced landsliding, liquefaction, and surface rupture. These zones indicate where the hazard may exist. Sites of proposed construction (new or remodel) within a zone must be investigated for the hazard. These maps are also used in real-estate transactions&emdash;disclosure is required if a property is within any of these hazard zones. CGS seismic hazard zone maps for the Bay Area are available at http://www.consrv.ca.gov/cgs/geologic_hazards/regulatory_hazard_zones/index.htm

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